Slide projectors



June 21, 1955 T. s BRISKIN- E T AL SLIDE PROJECTORS Filed Jan. 7, 1954 8 Sheets-Sheet 2 T.. s. BRISKIN ETAL 2,711,118

June 21, 1955 SLIDE PROJECTORS 8 Sheets-Sheet 3 Filed Jan. 7, 1954' 172%72507 5: lz eodare SEE/"1.91112 fozer'f Z. jyo are June 21, 1955 T. s. BRISKIN ETAL SLIDE PROJECTORS 8 Sheets-Sheet 4 Filed Jan. 7, 1954 a n 2, m 0 5; a 55 a N E j Y 5 .w ,W 5%

a Z W 2% June 21, 1955 T. s. BRISKIN ETAL 2,711,118 I SLIDE PROJECTORS I Filed Jan. '7, 1954 8 Sheeis-Sheet 5 jiz Jezzrzs meodore $329316): 06?! 1. Moore June 21, 1955 T. s. BRISKIN ET AL SLIDE PROJECTORS 8 Sheets-Sheet 6 Filed Jan. '7, 1954 .1 Jazz (a/'5 7360 40/42 5 3773111": $06272 Z floor'e 39 lzeys June 21, 1955 T.s. BRISKIN ET AL SLIDE PROJECTORS 8- Sheeis-Sheet 7 Filed Jan. 7, 1954 lhiwlln 1 1 II II I -L June 1,. 1955 "r. s. BRISKIN ETAL 2,711,113

SLIDE PROJECTORS Filed Jan. '7, 1954 8 Sheets-Sheet 8 United States Patent SLIDE PROJECTORS Theodore s. Briskin and Robert L. Moore, Chicago, m. assignors to Revere Camera Company, Chicago, Ill.', a corporation of Delaware Application January 7, 1954, Serial No. 402,654

10 Claims. (Cl. 88-27) into projecting position, will be illuminated so that the operator can view the same in an upright position.

Another object is to provide a slide projector having a more compact arrangement and which avoidsthe use of the usual vertically arranged lamp chimney. The usual vertical lamp chimney is objectionable for the reason that the face of the operator is oftentimes above the chimney in a position where it is subjected to the heat and light emanating from the chimney. The present arrangement avoids this objection with the result that the operators face may be located at any convenient position from which the slide may be viewed.

A further object is to provide a projector embodying improved slide supporting means whereby the transparency will be maintained in the proper focal plane irrespective of its thickness. The variation of thickness arises due to the fact that some transparencies are mounted in merely a cardboard frame, whereas others are sandwiched between sheets of glass. p

A still further object is to provide a projector embodying improved shutter means. In this connection a shutter is provided which has a symmetrical wipe action, thus providing a desirable and attractive fade-out and a fade-in.

Still another object is to provide, in a slide projector of the type delineated, a common control means for actuating both the slide carrier assembly and the shutter mechanism.

A further object is to provide means for actuating the shutter in such a manner as to avoid motion of the projected image.

Other objects, features and advantages will become apparent as the description proceeds.

With reference now to the drawings in which like ref.

erence numerals designate like parts:

Fig. l is a plan view of a preferred embodiment of this invention, the cover being removed;

Fig. 2 is a vertical longitudinal section taken along line 22 of Fig. 1, a portion of the cover being shown in dotted lines;

Fig. 3 is a vertical transverse section taken along line 33 of Fig. 2, but also showing the cover in dottedlines;

Fig. 4 is a vertical section taken along line 4-4 of Fig. 3 showing the construction of the slide carrier;

Fig. 5 is a plan view of Fig. 4;

Fig. 6 is a vertical longitudinal section taken along line 2 Fig. IO'isadetaiI section taken along line 10- 10 0 Fig. 6

ofFig.4;- 1

Fig. 12 is a transverse section looking rearwardly substantially along theline v12 12 of Fig. 2, but showing just the mechanism assembly;

Fig.'l3 is a rear elevation of the masking plate and shutter mechanism;

Figs. 13a and 13b are detail views of portions of the shutter blades;

Fig. 14 is a diagrammatic representation of the general arrangement of the parts, and

Fig. 15 is a perspective view of a portion of a slide support.

The mechanism of theprojector shown is mounted in,

and partially enclosed by, a box-shaped casing 20, as shown in Figs. 2 and 3. Suitably secured to the upper edges of the casing is a closure member '21 which is in the form of a die casting. The upper surface of the closure member forms the uppersurface of the projector. This upper surface may be divided into several portions, including a rear cylindrical portion 22, a front table 23 and a frontcylindrical portion 24. The rear cylindrical portion 22 is in the form of a cylinder about a', transverse axis and the front cylindrical portion 24 is in the form of a cylinder about the longitudinal. axis. The term longitudinal" as used herein indicates a-idirection. parallel to the axis of the optical system. A lens unit 25 is tele-. scopically accommodated within the front cylindrical portion 24.

The rear cylindrical portion v22 has formed therein an opening 26 through which. is exposed a portion .of a slide carrier assembly indicated generally by the reference numeral 27, and shown in detail inFigs. 4 and 5. A second opening 28 is formed in the portion 22 through which projects a portion of an actuating drum 29 by means of which the slide carrier assembly 27 is rotated. A recess 30 may be formed in the front table portion 23 to accommodate the group of slides being shown.

The casing 20 is provided with rear feet 3lzand-with an adjustable front foot 32. A suitable control member 33 for the adjustablefront foot 32extends through the closure member 21 so that the angle of projection can be conveniently regulated. A suitable cover 34 may be removably mounted on the marginal edges of the closure member 21, as shown by dotted lines in Figs. 2 and 3. This cover 34 cooperates with the casing 20 to-provide a convenient carrying case for the projector. Suitable latch means, not shown, may

be provided to secure the cover tothe casing 20.

The general arrangement of the projector is shown diagrammatically in Fig; 14. The slide .carrier'assembly 27 includes a ring 40 on which is mounted a' plurality of spaced slide supports 41 which extend toward the observer as seen in Fig. 14. The ring 40 is rotatably supported by a plurality of rollers 42. A lamp 43 extends through the ring 40 into the area between the slide sup-' ports, and is surrounded by .a lamp chimney 44 having formed therein an opening 4'5. Suitable projection lenses 46, adjustably mounted in the'lens unit 25, are spaced forwardlyof the lamp 43 and opening 45 and provide a path for thelight beam which is to be projected. One of the slide supports .41 is normally disposed in the path of this light beam so that an image may be projected on the usual projection screen, not shown. Disposed between the slide carrier and the projection lenses 46' is a shutter 47. Disposed between the lamp chimney'44 and the uppermost slide support 41 is a ground glass diffuser 48 which serves to illuminate the slide carried in the uppermost slide support so that it may be viewed by'the operator prior to projection.

Fig. 11 is a detail section taken along line 11-41 In operation, it will be seen that the slide is first placed in the uppermost slide support 41, in which position it is illuminated and can be viewed in upright position by the operator who is standing above and at the rear of the projector. Then the slide carrier is rotated 90, which brings the first slide into the path of the light beam in its proper inverted position so that it will be projected on to the projection screen. A second slide is then placed in the next adjacent slide support, which is then in the uppermost position, while the first slide is being projected, and so on, until the first-mentioned slide support again reaches the uppermost position. In other words, the present arrangement provides a loading and viewing station, a projecting station, and two storage stations which permit a previously projected slide to be re-projected. When the slide, after loading, again reaches the loading station, it is removed from its slide support and another slide substituted therefor.

Although the present embodiment shows four such stations, obviously three stations or five stations can be provided if it is desired to locate the loading stations at a somewhat different angle for convenience in view ing the slide to be loaded, such as an angle of 120 or 144, counterclockwise from the projecting station.

The construction of the slide carrier assembly is shown in Figs. 4, and 15. The slide supports 41 each comprise a stamping 50, and portions of adjacent connecting members 62. As shown in Fig. the stamping is provided with a rear flange 51 by means of which this element may be secured to the ring 40. The stamp- As shown in Figs. 4 and 5, a V-grooved roller 57 is f.

carried by a hub member 58 which is slidably mounted in the slot 55. A spring 59 bears against the roller 57 and urges the same outwardly away from the ring 40. The spring 59 is carried by a suitable pin 60 which is mounted in the rivet hole 56.

As shown in Figs. 4 and 15, shelf portions 61 are provided adjacent the wall portions 53, these shelf portions constituting marginal portions of the connecting members 62 which may also be in the form of sheet metal stampings. As shown in Figs. 5 and 3, the shelf portions terminate in V-shaped portions which cooperate with the V-grooved roller 57 to hold a slide in a centered position, that is, in a position which is symmetrical with respect to a plane which connects the apices of the .5

Vs provided by the roller 57and the portion 63. Thus, irrespective of the type of slide or of the thickness of its marginal portions, the transparency can be main tained in a centered position which corresponds to the focal plane of the optical system. a

The connecting members 62 are also suitably secured to the ring 40, as by rivets and they may be riveted or spot welded to the horizontal flanges 54 of the stampings 50 to provide a reinforced generally cylindrical structure which projects outwardly from the ring 40.

The outer edge of web portion52 is provided with a reinforcing flange which also acts as a filler to prevent inadvertent insertion of a slide between the web portion 52 and the closing member 21.

The slide carrier assembly 27 also includes detent means to cause it to seek an angular position in which the slide supports are maintained in their proper loading and projecting stations. This detent means includes a cam ring 70, shown in Fig. 6 which is secured to and supported from the ring 40 by pillars 71, as shown in Fig. 10. The cam ring is provided with notches 72 as shown in Fig. 6. A detent roller 73 is carried by an arm 74 which is pivoted at 75 on a frame plate '76. A suitable spring 77, shown in Fig. 9 engages a portion of the arm 74, to urge the detent roller. 73 into the notches 72 of the cam ring 70. In the embodiment shown,

there are four equidistantly spaced notches 72 which correspond to the four stations provided for the four slide supports 41. Thus, the slide carrier assembly is positively maintained in any one" of four angular positions. 5 As shown in Figs. 3 and 11, the frame plate 76 is provided with four pillars 80 on which the rollers 42 are is supported from the frame plate 76.

rotatably mounted. Thus, the slide carrier assembly 70 Screws 81, as shown in Figs. land 11, take into the 7 and 3, maintains these three lens assemblies in positionfi Upon removal of the retainer clip, the lens assemblies may be withdrawn bya transverse sliding movement, for

cleaning or replacement. A reflector is also mounted at the rear of the framework 82. j J g The framework 82 also serves as a support for the diffuser'48, which is spaced above the top member of the framework. Although the lamp chimney 44 shields the diffuser 48 from the directrays of the lamp, there is nevertheless considerable light leakage which strikes the ground glass of the diffuser and causes the same. to act loading station.

As shown in Figs. 3, 9 and 12, a blower 87 is also mounted on the frame plate 76 by means of a bracket 88. It draws 'air from right to left, as shown in Fig; 3, through the intake and outlet grills 98 and 99 to cool the lamp 43. To this end the frame plate 76 is provided with an opening 89 which is of a diameter approximating the inner diameters of the ring 40 and cam' ring 70. The bracket 88 includes a half duct portion 88:: which co-' 1 operates with an upper half duct member 90 to sur round the fan blades 91 of the blower 87 to provide im proved blower efliciency. v

The frame plate 76 is provided with lugs '92 as shown 4 in Figs. 6 and 9 on which the pillars 80 are mounted.

is preferably a stamping so that the lugs 92, arms and plate 94 constitute one integral member; 50

elements associated with the slide carrier assembly 27,

the framework 82, the lamp 43, and the blower 87 are supported from the frame plate 76, the blower 87 project- 66 ing from one side of the frame plateand the remaining secured, by means of a flange 10 2 and rivets 103' to the:

frame plate 76. Pivotally' mounted on the masking plate. by means of pivots'106, 107 are shutter blades 47a and 65 47b. A guide plate 108 is secured in spaced relation ship to the upper portion of the masking plate by: shoulder rivets 109. As shown in Fig. 2, the shutter blades and the guide plate 108are on the rear side of the masking plate, and the upper ends of the shutter blades 70 move from an open position shown inFig. 12 to a closed position shown in Fig. 13 in which the opening 101 is covered. This is a scissors type movement which pro- 75 duces a symmetrical V-shaped fade-out andfade-in, The i V as a source of illumination for viewing a slide in the Arms 93 extend from three of the lugs to support plate 94 on which the lamp base and lamp socket '96 ,are mounted, as shown in Fig. 3. The frame plate 76 To summarize the structural arrangement,all of the elements projecting from the other side of the frame elei V ments. Thus, a single assembly is provided, as shown extend into the space between the guide plate 108 and the masking plate 100. Thus, the shutter blades may awaits middle shoulder rivet 109 serves as a stop for the-two" shutter blades 47a and 47b.

The shutter blades overlap each other, and the means for moving them simultaneously are shown in 'Figs. 13, 13a and 13b. The lower end of each blade is provided with a slot 110, and 111, respectively, which is offset a substantial distance from the pivots 106 and 107, respectively. These slots overlap eachother and a pin 112, carried by lever 113, extends through both of the slots; The masking plate is provided with a suitable opening 117 to accommodate the outer end of the pin 112.

A spring 114 biases the lever 113 into shutter closed position as shown in Fig. 13. The lever 113 is pivoted on the shoulder of a pivot serew' 115 which has an eccentric shank 116, the shank being'screwed 'into or riveted to the masking plate 100. Thus, thefulcrum of the lever 113 may be shifted for purposes of proper adjustment.

In operation, it will be seen that elevation of the lug 118, integral with the end of lever 113, against the bias of spring 114 will cause the shutter blades 47a and 47b to move into the open position shown in Fig.12. When the lug 118 is not thus supported in its elevated position, the shutter blades are closed.

Common means are provided for rotating the slide carrier assembly 27 and to actuate the shutter mechanism,

this means comprising the actuating drum 29and its asand 8, projects from the second cam ring 123 and extends through a slot 125 formed in the first cam ring 70' so as to limit the extent of the lost motion.

The actuating tlrum 29, as shown in Figs. '3 and '8, is provided with an inwardly directed flange 126 to which the second cam ring 123 is suitably secured in spaced relationship by means of spacers 127. Thus, rotation of the actuating drum will .rotate the second cam ring 123 independently of the slide carrier assembly until such time as the lost motion is used up, and thereafter, the slide carrier assembly will rotate with the drum. The actuating drum 29 is provided with finger depressions 128 on its periphery.

As shown in Figs. 6 and 7, the cam 11118123 is provided with a plurality of equally spaced notches 130.

which serve as cam surfaces to displace a follower 131 which is carried by an arm 132. The follower is in the form of a flanged roller which rides on the inner edge of the cam ring. The arm 132 is pivoted on a pivot memher 133, shown in Fig. 9, which projects outwardly from the frame plate 76. Thus, the outer end 134 ofthe arm 132 moves downwardly as the follower is forced out of the of the closure member or die casting 21.

125, after allowance is made for the diameters of the follower 131 and the pin 124, respectively, so that the shutter 47' will be closed prior to the time that the lost motion connection initiates movement of the slide carrier assembly 29. Thus, when the parts rotate together, the actuating drum will be somewhat in advance of the slide carrier assembly. The follower 131 and notches also serve as aidetent which indicates the arrival of the actuating drum in its next normal position. The notches 72 have an effective angular width which issufiiciently greator than the effective angular width of the notches 130 so that the detent mechanism associated with the cam ring 70 will cause the slide carrier assembly 27 to continue its movement up to' and into normal position, even though the actuating drum 27 is not being rotated.

To accomplish thisresult, the effective width of the notch 72 should be more than twice the effective width of the notch 130. These angular distances have been related to the effective width of the notches and of the slot 125, but they can, with equal validity be related to the effective arc length of the rise portion provided by the forward half of the notch 130, with respect to the amount of lost motion provided forwardly of the normal position, for the purpose of closing the shutter. purpose of opening the shutter, these angular distances could be related to the arc length of the drop surface provided by the rear half of the notch 130 with respect to the arc length of the drop surface provided by the rear half of thenotch 72, this ratio being less than 1:2.

As indicated above, the term effective arc length represents the length of arcwith respect to the horizontal axis of the drum, after the. arc length of the radius of a particular follower has been subtracted.

As shown in Fig. 12 all of the mechanism constitutes a single assembly which is secured to the frame plate-76. This assembly is secured in its entirety to the underside w b To this end, the bracket 88 is provided with flanges of substantial length, and the masking plate 100 is also provided with a flange or lug141. Screws 142, shown only in Fig. 12, pass through suitable openings in the flanges 140, 141 and take into bosses, not shown, cast into the underside of the die'casting 21. Then the mechanism and die casting can be placed on the edges of the casing 20 and secured thereto by screws 143 shown in Fig. 1.

The lens unit 25, which is slidably received within the front cylindrical portion 24, is provided with a shallow screw thread 144. ,A click 145 suitably supported from the underside of the closure member 21, engages the screw thread to facilitate the focusing of the projection,

lenses. However, the click permitsstraight sliding movement of the lens unit to the approximate position desired. A semi-circular rib 146 formed on the under-surface of I the front cylindrical portion 24 serves as a second bearing notch 130 by rotation of the cam ring 123. A sprii1g135,

extending between the arm end 134 and a lug 136 formed in the masking plate 100 maintains the follower 131 in engagement with the cam ring.

The positions of the cam rings 70 and 123 shown in 134 of the arm 132 is maintained in elevated position by the spring 135, and this end engages the lug 118 of'the lever 113 to maintain the shutter blades '47a'and 47b in' open position, as shown in Fig. 12. r

Rotation of the second cam ring 123 will force the outer end 134 downwardly, and hence permit the shutter to close.

The effective angular width of the notches 130 is slightly less than the effective angular width of the slot point which cooperates with the click to maintain the lens unit in the desired axial alignment. The edge 147 formed by the opening in the front wall of the front cylindrical portion 24 constitutes the first bearing point.

To summarize the operation which has been described in detail in connection with the descriptionof the various assemblies and sub-assemblies, the projector is setup by removing the cover 34, and pulling out the lensunit 25 to approximately its desired position. Then the attachment cord, not shown, is plugged in to energize the motor and lamp circuits. A toggle switch 148 is provided in this connection.

When the parts are intheirnormal position, one slide support 41 will ,be inthe loading station and another will be in the projecting station. As the operator stands over and somewhat to the rear of the projector, and inserts a slide through the opening 26 and into a slide support 41, the slide will be illuminated by the diffuser 48 so that the operator can identify the same prior to movement into the projecting station. To insert the slide into the support, it is held by its right edge, looking down on Fig. 1,

For theand the left side of the slide is pushed against the V- grooved roller 57 to displace the same. Then the right edge of the slide can be slipped over the V-shaped portions 63, against which they will be held, in centered position, by the spring biased roller 57.

Then the actuating drum is rotated which will first close the shutter 47, and then move the slide carrier assembly into its next position, in which the slide will be maintained in the proper focal plane in the projecting station. Just as the actuating drum reaches its next position, the shutter will again be opened. However, the width of the notches 72 is sufficiently great that the detent mechanism causes accelerated movement of the slide carrier and will snap it into its proper position prior to the time that the normal motion of the actuating drum will cause the shutter to open. Thus, a symmetrical wipe or fade-out and fade-in is obtained at a time when the slide carrier is stationary, and there is no distracting motion of the projected image before the fade-out or'after the fade-in.

A fine focusing adjustment may be made by rotation of the lens unit and the angle of inclination of the projected beam may be adjusted by the control member 33.

In the arrangement shown, the actuating drum 29 and slide carrier assembly may be rotated in the reverse direction as well as in the forward direction. This feature, coupled with the fact that the slide carrier assembly holds more than two slides, provides the important advantage that the slide carrier assembly, at any time, may be reversed to project the previously projected slide. This arrangement avoids the ditficulties encountered when a member of the audience requests to see again the slide just projected, but the request is not made until after the previously projected slide has been removed from the slide carrier and replaced in the slide box.

By the same token, the drum may be reversed to show the second or third previously projected slide.

As heretofore pointed out, with the present invention, the operator can stand right over the projector, and still there will be no blast of hot air blowing in the operators face, nor will there be any bright beam of light shining in the operators eyes. It will be observed that the grilles are slanted downwardly with the result that the light will not be cast in an upward direction, and the air blast will be deflected downwardly on the table surface. v

At the conclusion of the projecting operation, there will still be three slides in the slide carrier assembly which must be removed by rotation of the actuating drum and the slide carrier. Then the lens unit can be collapsed into the front cylindrical portion 24, the attachment plug disconnected, and the cover 34 replaced and locked in place.

Although only a preferred embodiment of this invention has been shown and described herein, it will be understood that various modifications and changes may be made without departing from the spirit of the invention as pointed out in the appended claims.

We claim:

1. In a slide projector having a frame, a rotatable slide carrier assembly having a horizontal axis of rotationand including a plurality of slide supporting means spaced equally from each other and each arranged parallel to said horizontal axis, means for mounting saidslide carrier assembly for rotation about said horizontal axis, a lamp mounted on said frame and projecting into the space 2. The, combination claimed shield disposed between said translucent difluserjelement in said second slide supporting means is maintained 'in' said projecting station.

andsaidlamp. j r s r 3. A slide projector-comprising a frame, a rotatable slide carrier assembly having'a horizontal axis of rotation and including a plurality of slide supporting means equally spacedf from each other and each arranged.

parallel :to gthe horizontal axis, a ring connecting the same, and a detentcam, a plurality of rollers supported by saidframe, each on a horizontal axis, said rollers engaging said ringin supporting relationship to permit rotation of said slide carrier assembly with re-j spect to said horizontal axis, a spring-biased detent roller mounted on said frame and engaging said detent cam to cause said slide carrier assembly to stop in any one of a plurality of successive predetermined posi.

tions, and a lamp mounted on said frame and projecting through said ring and into the space bounded by said slide supporting means.

4. A slide projector as claimed in claim 3 in which one of said predetermined positions constitutes a loading station, and in which another of said predeter mined positions constitutes a projecting station, and a translucent diffuser element disposed between said lamp and said loading station. 3 V I 5. A slide projector as claimed in claim 4 including lamp and said projecting station.

6. A slide projector comprising a frame plate, a slide carrier assembly including a plurality of slide supporting means equally spaced fromeach other and each arranged parallel to a horizontal axis and a support ing ring, means for mounting said slide carrier assembly for rotation about said horizontal axis, said slide carrier assembly including a detent'cam supported from said ring, a spring-biased detent roller mounted on said frame plate and engaging said cam to cause said slide carrier assembly to stop in any one of a plurality of successive predetermined positions, a second cam. 7 lost motion means securing said second cam to saidslide carrier assembly, a follower for said second cam,

an actuating drum secured to said second cam so that said slide carrier assembly may be rotated bymanual rotation'of said actuating drum, means providing a light beam path, shutter means disposed in said light beam path, and means actuated by said follower for actuating said shutter means. i

7. A slide projector as claimed in claim 6 in which said lost motion means permits relative movement of said {slide carrier assembly and said actuating drum through a predetermined angular distance on either side of a normal position, said second cam having a notch providing a rise surface and a drop surface, the elfectivc arc length of said rise surface being not greater than said predetermined angular distance, and said first cam having, a notch providing a drop surface, the effective arc length of which is at least twice as great as that of said drop surface of said second cam.

8. Aslide projector as claimed in claim 6 in which said shutter means comprises a pair of overlapping shutter blades, means for pivotally mounting each of said shutter blades with respect to said frame, said follower actuated means including a lever mounted on said frame, and a pin mounted on said lever and engaging both of said shutter blades and actuating the same to provide a scissors-like pivotal movement whereby a substantially symmetrical V-shaped wipe is provided.

9. A slide projector comprising a frame including a vertically disposed frame plate having an opening therein and a'vertically disposed masking plate secured in clairrijl including a to said frame plate and perpendicular thereto, a slide carrier assembly rotatably mounted on and projecting from one side of said frame plate for rotation about a horizontal axis, a blower mounted on the other side of said frame plate opposite said opening, said slide carrier assembly including a plurality of slide supporting means spaced equally from each other and each arranged parallel to a horizontal axis, a lamp disposed within said slide carrier assembly near said horizontal axis, an opening in said masking plate, shutter means mounted on said masking plate, and manually operated common means for rotating said slide carrier assembly and for operating said shutter.

10. A slide projector comprising a slide carrier assembly including a plurality of slide supporting means equally spaced from each other and each arranged parallel to a horizontal axis and a ring connecting the same, a frame for said projector, a plurality of rollers supported by said frame, each on a horizontal axis, said rollers engaging said ring in supporting relationship to permit rotation of said slide carrier assembly with respect to said horizontal axis, said slide supporting means comprising a member providing a V-shaped groove for receiving one edge of a slide, a V-grooved roller for receiving the opposite edge of a slide, means for mounting said roller for movement toward and away from said groove providing member, and spring means engaging said roller for urging same into engagement with said opposite slide edge.

References Cited in the file of this patent UNITED STATES PATENTS 751,561 Roever et al. Feb. 9, 1904 1,071,708 Cone Sept. 2, 1913 1,354,823 Gilmore Oct. 5, 1920 1,537,654 Nash May 12, 1925 1,594,267 Jones July 27, 1926 1,605,245 Lehmann Nov. 2, 1926 2,319,284 Zwirn May 18, 1943 2,568,895 McMaster et al. Sept. 25, 1951 

